JP2017208586A - Base station device and terminal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique improving the accuracy of a symbol replica when performing symbol level canceling at a receiver in a downlink non-orthogonal access.SOLUTION: An adder unit 804 adds signals in number exceeding the number of transmission antenna ports at an identical time and an identical frequency, so that transmission is made from one or a plurality of transmission antennas 808. The adder unit 804 adds signals which are generated in mutually different transmission methods. The signals, generated in the mutually different transmission methods, include a signal generated by spreading processing in a spreading unit 809, and a signal generated without the application of the spreading processing.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a base station apparatus and a terminal apparatus.

  With the recent spread of smartphones and tablet terminals, wireless traffic is increasing rapidly. Research and development of the fifth generation mobile communication system (5G) is being carried out to cope with the rapidly increasing traffic.

  In the downlink of LTE (Long Term Evolution) or LTE-A (LTE-Advanced), an access method called OFDMA (Orthogonal Frequency Division Multiple Access), in which a large number of narrowband carriers (subcarriers) are arranged so as to be orthogonal ( Orthogonal multiple access) is used. On the other hand, many non-orthogonal multi-access technologies have been studied as 5G access technologies. Non-orthogonal multi-access transmits a signal having no orthogonality on the assumption that reception processing such as interference canceller or maximum likelihood estimation is performed at the receiver. DL-NOMA (Downlink Non-Orthogonal Multiple Access) has been proposed as one of non-orthogonal multi-access for the downlink (Patent Document 1 and Patent Document 2). In DL-NOMA, a base station apparatus (also called eNB (evolved Node B) or base station) multiplexes modulation symbols addressed to different terminal apparatuses (also referred to as UE (User Equipment), mobile station apparatus, mobile station, or terminal). Then send. At this time, the transmission power of each modulation symbol is determined in consideration of reception power (reception quality) at the multiplexed terminal apparatus. The terminal device can extract only the modulation symbol addressed to itself by decoding and canceling the signal addressed to another terminal device among the multiplexed transmission signals. Note that a terminal device that cannot decode a signal addressed to another terminal device regards the signal addressed to the other terminal as noise, and performs demodulation and decoding. At this time, the base station apparatus determines an appropriate MCS (Modulation and Coding Scheme) for a terminal apparatus that cannot be canceled in consideration of deterioration of reception quality.

JP 2013-9288 A JP 2013-9289 A

  In DL-NOMA, it is necessary to demodulate and decode a signal addressed to another terminal and to notify the terminal that performs cancellation of the MCS of the other terminal. However, if the MCS of other terminals multiplexed by DL-NOMA is notified in addition to the MCS of each terminal, the amount of control information on the downlink increases, and the amount of information data that can be transmitted on the downlink decreases. There was a problem.

  The present invention has been made in view of such circumstances, and an object of the present invention is to perform the DL-NOMA system without canceling the MCS of another terminal without increasing the control information. -To provide a system capable of performing NOMA.

  A terminal apparatus and a base station apparatus according to the present invention for solving the above-described problems are as follows.

  (1) The base station apparatus of the present invention includes an addition unit that adds signals exceeding the number of transmission antenna ports at the same time and the same frequency, and transmits from one or a plurality of transmission antenna ports. Signals generated by different transmission methods are added.

  (2) Moreover, the signal transmitted by the base station apparatus of the present invention includes the signal generated by the different transmission method includes the signal generated by the spreading process and the signal generated without applying the spreading process. It is characterized by that.

  (3) Further, the different transmission schemes transmitted by the adding unit of the base station apparatus of the present invention include at least an SC-FDMA transmission scheme and an OFDM transmission scheme.

  (4) Further, the different transmission schemes added by the adding unit of the base station apparatus of the present invention include a transmission scheme for transmitting a plurality of streams and a transmission scheme for transmitting one stream.

  (5) Further, the different transmission schemes added by the adding unit of the base station apparatus of the present invention are determined based on the resource allocation information.

  (6) In addition, the terminal device of the present invention receives a signal in which signals generated by different transmission schemes exceeding the number of transmission antenna ports at the same time and the same frequency are added, and transmits the different transmission schemes. A demodulation processing unit that performs demodulation processing on at least one of them, a replica generation unit that generates a symbol replica by an output of the demodulation unit, and a cancellation unit that subtracts the symbol replica from the received signal It is characterized by.

  (7) Moreover, the terminal device of this invention is further provided with the de-spreading part which performs a de-spreading process with respect to at least 1 among the said different transmission systems.

  (8) Further, in the terminal device of the present invention, the demodulator outputs a soft decision value, and the replica generator generates a soft replica.

  According to the present invention, since it is possible to perform DL-NOMA without notifying the MCS of another terminal, it is possible to improve cell throughput or user throughput.

It is a figure which shows an example of a communication system. It is a figure which shows an example of the conventional transmission apparatus structure. It is a figure which shows an example of signal point arrangement | positioning addressed to the terminal device 103. FIG. It is a figure which shows an example of signal point arrangement | positioning addressed to the terminal device. It is a figure which shows an example of signal point arrangement | positioning of the signal which the base station apparatus 101 transmits. It is a figure which shows an example of a structure of an OFDM transmission process part. It is a figure which shows an example of the structure of the conventional receiver. It is a figure which shows an example of a structure of an OFDM received signal processing part. It is a figure which shows an example of the transmitting apparatus structure which concerns on 1st Embodiment. It is a figure which shows an example of the spectrum of the signal addressed to the terminal device. It is a figure which shows an example of the spectrum of the signal addressed to the terminal device. It is a figure which shows an example of the receiver structure which concerns on 1st Embodiment. It is a figure which shows an example of the transmitting apparatus structure which concerns on 2nd Embodiment. It is a figure which shows an example of the modification of the receiver structure which concerns on 2nd Embodiment. It is a figure which shows an example of the receiver structure which concerns on 2nd Embodiment. It is a figure which shows an example of the transmitting apparatus structure which concerns on 3rd Embodiment. It is a figure which shows an example of the receiver structure which concerns on 3rd Embodiment.

[First Embodiment]
The communication system in the present embodiment includes at least one base station device (transmitting device, cell, transmission point, transmitting antenna group, transmitting antenna port group, component carrier, evolved Node B (eNB)) and a plurality of terminal devices (terminal, Mobile terminal, reception point, reception terminal, reception device, reception antenna group, reception antenna port group, User Equipment (UE)).

  FIG. 1 is a schematic diagram illustrating an example of a downlink (forward link) of a cellular system according to the first embodiment of the present invention. In the cellular system of FIG. 1, there is one base station apparatus (eNB) 101, and there are a terminal apparatus 102 and a terminal apparatus 103 connected to the base station apparatus 101. Base station apparatus 101 multiplexes signals destined for terminal apparatus 102 and terminal apparatus 103, and transmits them on the same subcarrier.

  FIG. 2 is a block diagram showing an example of a transmitter configuration of a conventional base station apparatus 101 that performs DL-NOMA. In FIG. 2, the number of multiplexed signals is two. The information bits are input to the encoding unit 201-1 and the encoding unit 201-2, and error correction encoding is applied. The encoding units 201-1 and 201-2 may perform processing such as bit interleaving. The error correction coded bits are input to modulation section 202-1 and modulation section 202-2, and processing for converting the bit sequence into a symbol sequence is performed. Here, the generated symbols are QPSK, 16QAM, 64QAM, and the like, and the modulation unit 202-1 and the modulation unit 202-2 may be subjected to different modulation. Note that which modulation method is used is determined based on, for example, information related to MCS input from the scheduling unit 206. Furthermore, the information regarding the MCS of the terminal device is notified to each terminal device through the control information channel. Note that at least the terminal apparatus 102 is notified of information related to the MCS of the terminal apparatus 103 in addition to the MCS of the terminal apparatus 102. The outputs of modulation section 202-1 and modulation section 202-2 are input to power control section 203-1 and power control section 203-2, respectively. The power control unit 203-1 and the power control unit 203-2 perform power control so that the total value of the average power output from the modulation unit 202-1 and the modulation unit 202-2 becomes a predetermined value. This power control may be determined in advance, or is determined by the scheduling unit 206 in consideration of cell throughput or user throughput, and is performed according to values input to the power control unit 203-1 and the power control unit 203-2. It may be broken. Outputs of the power control unit 203-1 and the power control unit 203-2 are input to the addition unit 204. Adder 204 combines the inputs from power controller 203-1 and power controller 203-2. For example, when the output of the power control unit 203-1 is a QPSK symbol with high power (amplitude) shown in FIG. 3A, and the output of the power control unit 203-2 is a 16QAM symbol with low power (amplitude) shown in FIG. 3B think of. In FIG. 3, the horizontal axis is the I axis and the vertical axis is the Q axis, which represent the in-phase component and the quadrature component, respectively. In addition, although 4 symbol points are described for QPSK and 16 symbol points are described for 16QAM, one point is actually output depending on the encoded bit sequence output by the encoding unit 201-1 or 201-2. The When the signal candidate points of FIG. 3A and FIG. 3B are generated by the power control units 203-1 and 203-2, the signal candidate points as shown in FIG. The output of the addition unit 204 is input to the resource allocation unit 205. Resource allocation section 205 arranges the signal output from addition section 204 on a predetermined subcarrier according to the allocation information input from scheduling section 206. However, when resource allocation is different between the terminal apparatus 102 and the terminal apparatus 103, it is necessary to notify resource allocation of the multiplexed terminal apparatuses. In this example, a case will be described in which terminal devices to be multiplexed (signal addition) use a common resource allocation. In FIG. 2, all signals are added by the adder 204, but the present invention is not limited to this, and the output of the modulator 202-1 or the modulator 202-2 may be input to the resource allocator 205. Good. The output of the resource allocation unit 205 is input to the OFDM signal generation unit 207. The output of the OFDM signal generation unit 207 is input to the terminal device 102 and the terminal device 103 via the transmission antenna 208.

  An example of the configuration of the OFDM signal generator 207 is shown in FIG. The OFDM signal generation unit 207 generates an OFDM signal that is a multicarrier. The output of the resource allocation unit 205 is input to the IFFT unit 501. The IFFT unit 501 performs processing for converting a frequency domain signal into a time domain signal. The output of the IFFT unit 501 is input to the CP adding unit 502, and CP is added. The output of the CP adding unit 502 is input to the wireless transmission unit 503, and processes such as D / A conversion, filtering, up-conversion, and power amplification are applied. The output of the OFDM signal generation unit 207 is transmitted to the terminal device 102 and the terminal device 103 via the transmission antenna 208 of FIG.

  FIG. 6 shows a conventional example of the receiver configuration of the terminal apparatus 102 that receives a signal subjected to DL-NOMA. A signal received via the reception antenna 601 is input to the OFDM reception signal processing unit 602. An example of the configuration of the OFDM reception signal processing unit 603 is shown in FIG. The received signal is input to the wireless receiving unit 701, and processing such as down conversion, filtering, A / D conversion, and the like is performed. The output of the wireless reception unit 701 is input to the CP removal unit 702, and the CP inserted on the transmission side is removed. The output of the CP removing unit 702 is input to the FFT unit 703, and the time domain signal is converted to the frequency domain signal by the FFT. The output of the FFT unit 703 is input to the resource extraction unit 603 in FIG. The resource extraction unit 603 extracts a resource (subcarrier) in which a signal addressed to the terminal apparatus 102 is arranged. Note that information necessary for resource extraction is generated by the scheduling unit 206 in FIG. 2 and is notified to the terminal apparatus 102 through the control information channel separately from the information bits. Note that the control information channel refers to PDCCH (Physical Downlink Control Channel) or EPDCCH (Enhanced PDCCH) in LTE.

  The output of the resource extraction unit 603 is input to the channel compensation unit 604. The channel compensation unit 604 performs channel estimation using DMRS (Demodulation Reference Signal) or CRS (Cell-specific Reference Signal), and compensates the influence received on the propagation path (channel) using the obtained channel estimation value. . The output of the channel compensation unit 604 is input to the demodulation unit 605 and the cancellation unit 606. Demodulation section 605 performs demodulation using the modulation scheme used in terminal 101 (QPSK in the case of FIG. 3). As described above, the terminal device 102 is notified of the MCS of the terminal device 103. The output of the demodulation unit 605 is input to the decoding unit 607, and decoding is performed based on information related to the MCS of the terminal device 103. The information bit sequence addressed to the terminal device 103 obtained by decoding is input to the encoding unit 608 and re-encoded. Here, the coding rate is determined based on information related to MCS of the terminal apparatus 103. That is, the encoding unit 608 performs the same processing as the encoding unit 201-1 in FIG. The output of the encoding unit 608 is input to the modulation unit 609, and modulation is performed based on the information regarding the MCS of the signal addressed to the terminal apparatus 103. That is, the modulation unit 609 performs the same processing as the modulation unit 202-2 in FIG. The output of the modulation unit 609 is input to the power control unit 610. Here, the control value in the power control unit 610 may be notified from the base station apparatus 101 or may be estimated from a reference signal such as DMRS or CRS. That is, ideally, the power control unit 610 performs the same processing as the power control unit 203-2 in FIG. 2 and outputs the modulation symbols in FIG. 3A. The output of the power control unit 610 is input to the cancel unit 606. The cancel unit 606 subtracts (cancels) the signal addressed to the terminal device 103 output from the power control unit 610 from the signal input from the channel compensation unit 604, so that only the signal addressed to the terminal device 102, that is, ideal Then, the modulation symbol of FIG. 3B is obtained. The output of the cancel unit 606 is input to the demodulator 611 and demodulated based on the MCS of the terminal device 102. By applying error correction decoding to the output of the demodulation unit 611 by the decoding unit 612, an information bit sequence addressed to the terminal apparatus 102 is obtained.

  As described above, in the conventional DL-NOMA system, at least for a terminal device that is supposed to cancel a signal addressed to another terminal device, the MCS used by the other terminal device for communication is a base station device. Need to be notified. Of course, since the types of MCS are limited, it may be possible to try all the MCSs of other terminal devices, but considering the decoding process, the amount of calculation becomes enormous and not realistic.

  Therefore, there is a technique called SLIC (Symbol-Level Interference Cancellation) in which a signal destined for another terminal apparatus is not subjected to a decoding process, only a demodulation process is performed, a replica is generated based on a demodulation result, and a cancellation process is performed. . Since SLIC does not perform decoding processing, it is not necessary to know the coding rate of other terminals. Also, regarding the modulation schemes of other terminals, if there are about three types of QPSK, 16QAM, and 64QAM, it is possible to estimate from the statistical properties and the like, information on MCS of other terminals is notified from the base station apparatus. Without this, DL-NOMA can be introduced.

  However, when a replica is generated from a demodulation result instead of generating a signal replica of another terminal from the decoding result, it is assumed that the accuracy of the replica is bad and cancellation is not appropriately performed. Although there are terminals that can correctly demodulate signals of other terminals, such terminal devices need to have extremely high reception quality. As a result, the number of combinations of terminals that can perform DL-NOMA becomes limited, and the application effect of DL-NOMA also decreases.

  Therefore, in the present embodiment, at least a distant (low reception quality) terminal device among signals multiplexed by DL-NOMA is not based on OFDM, but by a transmission method in which a signal is spread in the frequency domain and / or time domain. Think about communicating.

  FIG. 8 shows an example of the transmitter configuration of the base station apparatus according to this embodiment. In FIG. 8, the number of signals multiplexed by DL-NOMA is two as in FIG. 2, but the present invention is not limited to this, and three or more signals may be multiplexed. Although the description will be made assuming that the number of transmission antennas is 1, it can be combined with existing multi-antenna technologies such as SU-MIMO (Single User Multiple Input Multiple Output) and MU-MIMO (Multi-User MIMO). The antenna may mean a physical antenna or an antenna constituted by a plurality of antennas. The latter is defined as an antenna port in 3GPP. Since FIG. 8 and FIG. 2 which is a conventional configuration differ only in whether or not the diffusion unit 809 exists, this point will be described. Note that the insertion position of the diffusion unit 809 is not limited to this, and may be after the modulation unit 802-2.

  The spreading unit 809 performs spreading on the output sequence of the power control unit 803-2. In the present embodiment, as an example of a spreading method, a case where spreading and multiplexing using a DFT matrix are performed will be described. Note that the present embodiment is not limited to this, and frequency spreading using a Walsh-Hadamard code, frequency spreading using an M sequence, that is, the output of the spreading unit 809 may be an MC-CDM (Multi-Carrier Code Division Multiplexing) signal. However, time spreading may be performed using these codes. Furthermore, frequency spreading and time spreading may be combined. That is, the spreading unit 809 outputs a signal such as DS-CDM (Direct Sequence CDM), MC-DS-CDM, or NxDFTS-OFDM, which is a signal to which DFT spreading is applied to each of a plurality of subbands (resource block group or resource block). Such cases are also included in the present invention.

  Next, input to the adding unit 804 will be described. The power amplifying unit 803-1 outputs a spectrum as shown in FIG. 9A. FIG. 9A shows an example in which a spectrum is composed of eight subcarriers. Here, the modulation symbols in FIG. 3A constitute each subcarrier.

  On the other hand, the spreading unit 809 performs spreading and multiplexing using the DFT matrix on the output of the power control unit 803-2, that is, the OFDM signal. In other words, a subcarrier with OFDM is spread with a corresponding column vector of the DFT matrix, and another subcarrier is spread with a corresponding another column vector. A transmission spectrum is generated by multiplexing the spread subcarriers. This is generally called DFT-spread-OFDM (DFT-S-OFDM). DFT-S-OFDM is also called DFT-precoded-OFDM, SC-FDM (Single Carrier Frequency Division Multiplexing), broadband single carrier transmission, or simply single carrier transmission. Thus, since the transmitter of the base station apparatus of this embodiment includes the spreading unit 809, FIG. 9A and FIG. 9B are multiplexed.

  Although the spreading unit 809 is provided only for the signal processing addressed to the terminal device 103 in FIG. 8, the present embodiment is not limited to this, and the spreading processing can also be performed on the terminal device 102. Here, the spreading process for the signal destined for the terminal apparatus 103 may be the same as the spreading process destined for the terminal apparatus 102, or may be based on the same standard (that is, the sequence number of the spreading code is different). The spreading area may be different in the time domain or the frequency domain.

  Next, the receiver configuration of the terminal device according to the present embodiment will be described. FIG. 10 shows an example. In FIG. 10, the processing up to the channel compensation unit is the same as in FIG. However, since the channel compensation unit 1010 also performs channel compensation for a signal that has been spread and multiplexed, it is necessary to apply a weight that takes into account this and that the OFDM symbol of the terminal apparatus 102 is multiplexed. Is desirable. In FIG. 10, the output of the channel compensation unit 1004 is input to the despreading unit 1010 and the cancellation unit 1006.

  In the despreading unit 1010, the despreading process corresponding to the diffusion unit 809 in FIG. 8 is applied. When DFT spreading is applied in the spreading unit 809 in FIG. 8, IDFT processing is applied in the despreading unit 1010. Symbols spread over a wide band by DFT processing can be synthesized by IDFT processing. For example, if the channel is frequency selective fading, the information transmitted on subcarriers with reduced gain in OFDM is erroneous due to noise, whereas in transmission with spread, there are subcarriers that have dropped. Even so, average quality can be obtained by despreading. This effect is generally called a frequency diversity effect.

  The output of despreading section 1010 is input to demodulation section 1005. Demodulation section 1005 performs demodulation processing on the signal addressed to terminal 103, that is, conversion processing using a soft decision value from a symbol sequence to a bit sequence. Here, it is not always necessary to notify the terminal apparatus 102 of which modulation scheme is transmitted, and it is possible to estimate which modulation scheme is used using existing technology. It is. The demodulator 1005 performs demodulation processing based on the estimated modulation method. Note that the modulation scheme may be estimated or reported from the base station apparatus 101. Although it is necessary to consider what kind of power control is applied in the base station apparatus 101, this may be notified from the base station apparatus 101 or may be estimated using a received reference signal. As described above, the influence of power control may be taken into account by the channel compensation unit 1004.

  The output of the demodulator 1005 is input to the replica generator 1007. The replica generation unit 1007 generates a symbol replica using the bit sequence input from the demodulation unit 1005. Here, the symbol replica may generate a hard replica from bit information obtained by hard-decision of the input soft decision bit sequence, or generate a soft replica corresponding to the likelihood of the input soft decision bit sequence May be.

  The symbol replica output from the replica generation unit 1007 is input to the power control unit 1008, and processing similar to that of the power control unit 610 in FIG. 6 is performed. The output of the power control unit 1008 is input to the diffusion unit 1009, where diffusion processing is performed. Here, the same processing as the diffusion processing performed in the diffusion unit 809 in FIG. 8 is applied to the diffusion processing. That is, in this embodiment, DFT processing is performed. The output of the diffusion unit 1009 is input to the cancellation unit 1006.

  The cancel unit 1006 subtracts the output of the spreading unit 1009 from the output of the channel compensation unit 1004. As a result, only the spectrum addressed to the terminal apparatus 102 can be extracted from the spectrum obtained by combining the spectrum addressed to the terminal apparatus 102 and the spectrum addressed to the terminal apparatus 103. For example, only the spectrum of FIG. 9A can be extracted from the spectrum obtained by synthesizing the spectrum of FIG. 9A and the spectrum of FIG. 9B.

  The output of the cancel unit 1006 is output to the demodulation unit 1011. Since the subsequent processing is the same as the conventional configuration shown in FIG.

  As described above, in the transmitter according to the present embodiment, a signal is generated by applying spreading to a remote terminal device (that is, a terminal device with low reception quality), and a nearby terminal device (that is, a terminal device with high reception quality) Add (synthesize) with the addressed signal and transmit. By applying spreading processing to the generation of signals destined for the remote terminal device, it is possible to obtain good transmission characteristics due to the frequency diversity effect due to spreading even when decoding is not applied to the signal processing of the remote terminal device in the nearby terminal device. it can. In other words, compared to the case where the spread processing such as OFDM is not applied to the remote terminal device, it is possible to generate a highly accurate replica when the error correction decoding is not applied, so that the cancel processing can be appropriately performed. become. As a result, many terminal devices can perform DL-NOMA communication, which increases cell throughput. Furthermore, in orthogonal multi-access such as FDMA, only one terminal device can be transmitted per subcarrier, whereas in DL-NOMA, multiple terminal devices share the same subcarrier for transmission. Therefore, the transmission opportunity of each terminal device increases. Therefore, user throughput can also be increased.

  Here, MU-MIMO has conventionally existed as a technique in which a plurality of terminal apparatuses share the same subcarrier, and MU-MIMO requires a plurality of transmission antennas, whereas DL-NOMA requires one transmission. Even with an antenna, two or more terminals can transmit by sharing the same subcarrier at the same time. Furthermore, it is possible to combine DL-NOMA and MU-MIMO, and in this case, the present invention is also effective.

  Further, when a single carrier signal is generated by using DFT in spreading section 809, the PAPR (Peak to Average Power Ratio) of the transmission signal can be lowered as compared with OFDM. As a result, it is not necessary for the base station apparatus 101 to include an expensive amplifier, so that a low-priced base station apparatus can be manufactured. This effect becomes more prominent as the number of antennas (or the number of antenna ports) increases.

  In FIG. 8, the adding unit 804 is arranged before the OFDM signal generating unit 807, but may be arranged after the OFDM signal generating unit 807. That is, the addition process may be performed in the time domain. Here, the addition processing in the time domain indicates that an addition unit is arranged after the IFFT unit 501.

  In addition, when multiplexing 3 or more terminal devices, when each terminal performs spreading processing, it is best to calculate the expected throughput in consideration of the case where it is not performed, and perform communication by the multiplexing method with the highest value. Characteristics can be obtained. However, since the above method has a problem that the calculation amount becomes enormous, even if the condition that the spreading process is applied only to the terminal farthest away and the spreading process is not performed on the other terminal devices may be added. Alternatively, the condition that the spreading process is not applied only to the terminal device located closest to the other terminal devices may be added.

[Second Embodiment]
In the first embodiment, it has been shown that spreading processing is applied to a remote terminal device (that is, reception quality is low). This considers the following two points. First, compared to a transmission method that does not perform spreading such as OFDM, a transmission method that performs spreading reduces the coding gain due to inter-symbol interference caused by frequency selective fading. Transmission characteristics generally deteriorate compared to OFDM. Secondly, at the time of non-coding, since the transmission method that performs spreading can obtain the frequency diversity effect, it can obtain better transmission characteristics than OFDM that cannot obtain the frequency diversity effect. That is, it is used that the transmission characteristics of the transmission system that performs spreading and the transmission system that does not perform spreading are reversed depending on the presence or absence of error correction coding.

  In other words, the present invention can be applied to two, three, or more systems in which superiority and inferiority are reversed depending on the presence or absence of error correction coding. In the present embodiment, a case where the present invention is applied between MIMO transmission and SIMO transmission will be described.

  As a method of transmitting data using a plurality of transmission antennas, MIMO transmission (so-called SU-MIMO transmission) for transmitting a plurality of streams (layers) and a method of transmitting only one stream with increased reliability (so-called transmission antenna diversity, There are also two techniques (transmission diversity). Here, for example, in the case of 2 transmission antennas, when transmitting 2 streams, QPSK, when transmitting only 1 stream, when transmitting 16 QAM, the same data rate is obtained. Compared to MIMO transmission using coding with strong error correction capability, transmission diversity without error correction coding has better characteristics. This is 16QAM at the time of transmission diversity, the distance between signal points is narrow, and the absolute value of a bit LLR (Log-Likelihood Ratio) obtained at the time of demodulation is smaller than that of QPSK. On the other hand, in the case of MIMO transmission, if the signal can be appropriately separated by processing (spatial filtering) at the receiver (that is, after spatial filtering), since QPSK demodulation is performed, an LLR having a large absolute value can be obtained. If the signals cannot be properly separated, an LLR having a small absolute value (or a positive / negative error) is obtained. In general, error correction is performed more favorably in MIMO transmission because the coding gain is higher as the variation in LLR is larger.

  In addition, when error correction is not performed, that is, when encoding is not performed, the characteristics of subcarriers with low orthogonality are hampered when a plurality of streams are transmitted as described above, while there are few positive and negative errors during transmission diversity. Bit LLR is obtained. As a result, as the error rate characteristic of the coded bit obtained by making a hard decision on the output LLR of the demodulator, the characteristic of MIMO transmission that transmits a plurality of streams may be deteriorated more than the characteristic of transmission diversity. In addition, when transmission diversity is performed, there is a gain due to transmission diversity, so that good transmission characteristics can be realized without decoding.

  Therefore, in the present embodiment, an example is shown in which DL-NOMA is configured after applying transmission diversity having good characteristics at the time of non-coding to a remote terminal device (that is, reception quality is low).

  An example of the transmitter configuration of the base station apparatus of this embodiment is shown in FIG. An example will be described in which MIMO transmission is performed for the terminal apparatus 102 in FIG. 1 and transmission diversity is performed for the terminal apparatus 103. Note that FIG. 11 illustrates the case where the number of transmission antennas is two, but the case where transmission is performed using three or more transmission antennas is also included in the present embodiment. The information bit sequence addressed to the terminal device 102 is input to the encoding unit 1101-2, and the information bit sequence addressed to the terminal device 103 is input to the encoding unit 1101-1. While the output of the encoding unit 1101-1 is input to the modulation unit 1102-1 as it is, the signal addressed to the terminal apparatus 102 performs MIMO transmission, so the output of the encoding unit 1101-2 is input to the S / P modulation unit 1109. It is input and S / P (Serial to Parallel) conversion is performed. In the present embodiment, S / P conversion is performed after encoding. However, the present embodiment is not limited to this, and S / P conversion may be performed before encoding.

  The output of the S / P converter 1109 is input to the modulators 1102-2 and 1102-3. Modulating sections 1102-1 to 1102-3 convert bit sequences into symbol sequences by the modulation scheme specified by scheduling section 1106. Outputs of the modulation units 1102-1 to 1102-3 are input to the power control units 1103-1 to 1103-3, respectively. In power control sections 1103-1 to 1103-3, control is performed so that power between layers of MIMO transmission and power between signals multiplexed by DL-NOMA become appropriate values. For example, in order to make the transmission power between layers the same, the power given by the power control section 1103-2 and the power control section 1103-3 may be made equal. The output of the power control unit 1103-1 is input to the duplication unit 1110, and the outputs of the power control unit 1103-2 and the power control unit 1103-3 are input to the addition unit 1104-1 and the addition unit 1104-2, respectively.

  The duplicating unit 1110 duplicates the input signal and inputs it to the adding unit 1104-1 and the adding unit 1104-2. Adder 1104-1 adds (synthesizes and sums) the input from duplicating unit 1110 and the input from power control unit 1103-2, and outputs the result to precoding unit 1111. Adder 1104-2 adds (synthesizes and sums) the input from duplicating unit 1110 and the input from power control unit 1103-3, and outputs the result to precoding unit 1111. Through the processing in the adders 1104-1 and 1104-2, the signal addressed to the terminal device 103 and the signal addressed to the terminal device 102 are transmitted by DL-NOMA. In FIG. 11, the duplication unit 1110 is configured to input a signal addressed to the far terminal apparatus to both of the two inputs to the precoding unit 1111, but the duplication unit 1110 may not be provided. For example, the transmitter configuration is as shown in FIG. In the case of FIG. 12, the output of the power control unit 1203-1 is input only to the addition unit 1204. That is, in order to improve the reception quality in the remote terminal apparatus 102, the power control unit 1203-1 performs control so as to allocate more power than other power control units.

  In the precoding unit 1111 to which the outputs of the adder 1104-1 and the adder 1104-2 are input, precoding processing is applied. Here, the precoding process is, for example, a process of multiplying a matrix such as a unit matrix, a DFT matrix, a Walsh-Hadamard matrix, a House-Holder matrix, and the like. May be selected. Further, when the number of transmission antennas is larger than the number of transmission layers, that is, the number of inputs to precoding, a configuration in which a transmission diversity effect is obtained by combination with an Alamouti code or the like may be adopted.

  The output of precoding section 1111 is input to resource allocation section 1105-1 and resource allocation section 1105-2, respectively. Since the subsequent processing is the same as that of the first embodiment, description thereof is omitted. Although not shown in FIG. 11, it is necessary to transmit a reference signal in order to perform channel estimation in the receiver, but the same precoding as that of data is applied to the reference signal. However, when the receiver can grasp the precoding on the transmission side, the reference signal may be transmitted without performing the precoding.

  As described above, according to the transmitter configuration of the base station apparatus shown in the present embodiment, a signal is transmitted to the terminal apparatus 103 having low reception quality (distant) by transmission diversity, and the terminal apparatus 102 having high reception quality (neighboring). On the other hand, a plurality of streams are transmitted using a plurality of transmission antennas while performing multiplexing by the terminal device 103 and DL-NOMA with some streams. As a result, even when the SLIC is used, it is easy to cancel a signal addressed to a distant terminal device in a nearby terminal device, so that the application effect of DL-NOMA is improved.

  Next, the receiver configuration of the terminal device 102 according to the present embodiment, that is, the neighboring terminal device will be described. FIG. 13 shows an example of the configuration. Reception signals received by the reception antennas 1301-1 and 1301-2 are input to OFDM reception processing units 1302-1 and 1302-2, respectively. The configurations of the OFDM reception processing units 1302-1 and 1302-2 are the same as those described in FIG. The outputs of the OFDM reception processing units 1302-1 and 1302-2 are input to the resource extraction units 1303-1 and 1303-2, respectively. The resource extraction units 1303-1 and 1303-2 extract the subcarriers used for communication in the same manner as in FIGS. Outputs of the resource extraction units 1303-1 and 1303-2 are input to the MIMO separation unit 1304. The MIMO separation unit 1304 performs a process of separating the transmission signal combined in the channel. Here, any separation method in the MIMO separation unit 1304 may be used, spatial filtering such as MMSE or ZF may be used, and detection based on MLD may be performed. Note that channel estimation values used for spatial filtering, MLD, and the like are performed by a channel estimation unit (not shown).

  The output of MIMO separation section 1304 is input to demodulation section 1305-1 and demodulation section 1305-2. Demodulator 1305-1 and demodulator 1305-2 perform symbol demodulation processing based on the modulation scheme applied by modulator 1102-1 and the power applied by power controller 1103-1. Outputs of the demodulation units 1305-1 and 1305-2 are input to the synthesis unit 1309. A combining unit 1309 combines or selects likelihoods of bit sequences input from the demodulation units 1305-1 and 1305-2. The output of the synthesis unit 1309 is input to the replica generation unit 1307. The replica generation unit 1307 generates a symbol replica.

  As described above, since the signal addressed to the remote terminal device 103 is transmitted in two layers, the bit sequence is improved by combining the bit sequence according to the likelihood in the combining unit 1309. be able to.

  The output of the replica generation unit 1307 is input to the power control unit 1308. The power control unit 1308 performs processing similar to that of the power control unit 1103-1 in FIG. 11, and the obtained signals are input to the cancellation units 1306-1 and 1306-2, respectively.

  Cancellers 1306-1 and 1306-2 subtract the output of power controller 1308 from the output of MIMO separator 1304. By this processing, only the signals output from the power control unit 1103-2 and the power control unit 1103-3 can be extracted from the signals synthesized by the addition units 1104-1 and 1104-2 in FIG. Since the subsequent processing is the same as that of the first embodiment, description thereof is omitted.

  The outputs of cancel sections 1306-1 and 1306-2 are input to demodulation sections 1311-1 and 1311-2, respectively, and demodulation processing is performed in consideration of control by power control sections 1103-2 and 1103-3. Bit sequences obtained by the demodulation processing are respectively input to the decoding units 1112-1 and 1112-2, and the decoding processing is performed based on the coding rate notified from the base station. Decoding sections 1112-1 and 1112-2 output the bit sequence obtained by decoding as information bits.

  As described above, in the receiver of the terminal device according to the present embodiment, regarding the transmission of the signal addressed to the remote terminal device, since the same signal is transmitted instead of transmitting a different signal, synthesis is performed in the receiver. This can increase the likelihood of bits. As a result, it is possible to generate a highly accurate symbol replica even when decoding is not performed. As a result, the number of terminals capable of canceling the signal of the remote terminal device increases, so that the application effect of DL-NOMA can be enhanced.

  In the present embodiment, a case is shown in which the same symbol is duplicated and transmitted with different precoding in order to obtain a gain by transmission diversity. However, as described with reference to FIG. 11, the bit likelihood can be improved in the case where error correction is not performed by increasing the transmission power of the remote terminal apparatus without performing replication. That is, the present invention includes a technique for improving received power by performing one-layer communication without performing MIMO transmission to a remote terminal apparatus.

[Third Embodiment]
In the first embodiment, a base station apparatus that applies spreading processing to a signal addressed to a remote terminal apparatus has been described. When spreading processing is performed in the base station device that is a transmitter, it is necessary to perform despreading processing in the terminal device that is a receiver. When DFT is used for spreading processing, IDFT is used as despreading processing. In this case, it becomes a problem for which subcarrier IDFT processing is performed. When resource allocation differs between terminal devices participating in DL-NOMA, it is conceivable to notify a nearby terminal device of a DFT section (that is, allocation information) of a signal addressed to a remote terminal device. Control information is increased.

  Thus, when spreading is performed on a signal addressed to a remote terminal device, it can be considered that the allocation of the remote terminal device and the resource allocation of the nearby terminal device are matched. In this case, if the nearby terminal apparatus applies the despreading process by allocating the signal addressed to the own apparatus, the adjacent terminal apparatus can perform the appropriate despreading process on the signal addressed to the other apparatus (far terminal apparatus).

  However, matching the resource allocation between the signal addressed to the remote terminal device and the signal addressed to the nearby terminal device limits the scheduling at the base station device, thereby reducing the cell throughput.

  Therefore, in this embodiment, a transmission method according to the first embodiment and a method of adaptively switching between the conventional transmission method according to the scheduling method will be described.

  FIG. 14 shows an example of the transmitter configuration of the base station apparatus according to this embodiment. Since the processes up to the power control units 1403-1 and 1403-2 are the same as those in the first embodiment, the description thereof is omitted. The output of the power control unit 1403-1 is input to the resource allocation unit 1405-1. Further, the output of the power control unit 1403-2 is input to the diffusion switching unit 1409. The spreading switching unit 1409 switches whether to perform spreading such as DFT or not based on the scheduling information input from the scheduling unit 1406. For example, in the LTE downlink, there are a method of assigning continuous resource blocks (continuous arrangement, resource allocation type 1) and a method of assigning resource block groups (subbands) discretely (discrete arrangement, resource allocation type 0). In general, since the frequency response of the channel is a frequency selective fading channel, a resource block with a high gain can be selected by performing a discrete arrangement. On the other hand, when the effect of scheduling is low, such as when the moving speed of the terminal is high, it is conceivable to apply continuous arrangement. Moreover, since notification information increases in order to perform discrete arrangement, it is conceivable that continuous arrangement is also applied when control information is desired to be suppressed.

  In the spreading switching section 1409, when the information input from the scheduling section 1406 is information indicating, for example, continuous arrangement, spreading processing is performed, and the signal after spreading processing is input to the resource allocation section 1405-2. On the other hand, when the information input from the scheduling unit 1406 is information indicating a discrete arrangement, a signal is input to the resource allocation unit 1405-2 without performing spreading processing. As described above, the diffusion switching unit 1409 determines whether or not to perform diffusion according to the scheduling-related information input from the scheduling unit 1406.

  Next, processing in the scheduling unit 1406 will be described. As described above, the scheduling unit 1406 determines whether to perform resource allocation continuously or discontinuously in consideration of the moving speed of 102 and the amount of control information of the remote terminal device 103 and the nearby terminal device. In the case of non-consecutive allocation, scheduling is applied independently to each terminal device. On the other hand, in the case of continuous allocation, scheduling is performed in a common and continuous arrangement for terminal devices participating in DL-NOMA. The scheduling result is input to the resource allocation unit 1405-1 and the resource allocation unit 1405-2.

  The processing in other blocks in the block diagram shown in FIG. However, for the addition unit 1404, addition processing is applied to the signal after resource allocation.

  Next, an example of a receiver configuration of the nearby terminal apparatus 102 according to the present embodiment is shown in FIG. FIG. 15 has substantially the same configuration as FIG. 10 except that it is not the despreading unit 1010 but the despreading switching unit 1515 and that it is not the spreading unit 1009 but the diffusion switching unit 1509. . Only these changes will be described below.

  The despreading switching unit 1515 determines whether or not to perform despreading according to the scheduling information notified from the base station apparatus 101. That is, when scheduling information is continuously arranged, signals spread in the same band are multiplexed, and thus a signal destined for a far terminal apparatus is obtained by despreading. Here, if the information on whether or not multiplexing by DL-NOMA is performed is not notified to the neighboring terminal device, the signal after despreading is a small value, and therefore the replica generation unit 1507 performs soft decision. By generating a replica, it is possible to avoid inappropriate cancellation processing. On the other hand, when the scheduling information is discretely arranged, a signal obtained by spreading a spread process in the same band is not multiplexed, and a signal that is not spread (that is, an OFDM signal) is not transmitted in each resource block. May be multiplexed. Therefore, whether or not multiplexing is performed for each received resource block is determined based on statistical properties or the like, and the resource block determined to be multiplexed is input to the demodulation unit 1505 as it is and multiplexed. The resource blocks determined not to be input are input to the demodulator 1505 with weighting so that the value becomes smaller or with a value of zero. In addition, in the case of discrete arrangement, information indicating which resource block is determined to be multiplexed is input from the despreading switching unit 1515 to the spreading switching unit 1509.

  Next, the diffusion switching unit 1509 will be described. The spreading switching unit 1509 determines whether or not to perform despreading according to the scheduling information notified from the base station apparatus 101. In the case of continuous arrangement, since spread signals are multiplexed, the spread switching unit 1509 applies spread processing. On the other hand, in the case of discrete arrangement, since the spread signals are not multiplexed and the signals that are not spread are multiplexed, the signals are arranged based on the multiplexed information input from the despreading switching unit 1515 and canceled. A signal canceled by the unit 1506 is generated.

  Thus, according to the present embodiment, the base station apparatus determines whether to apply the spreading process to the signal of the remote terminal apparatus based on the scheduling method. When a nearby terminal apparatus is notified of scheduling allocation and the resource allocation information indicates continuous allocation, a replica of a signal addressed to a remote terminal apparatus is generated by despreading, and the resource allocation information indicates discrete allocation Generates a replica of a signal addressed to a remote terminal device without performing despreading processing. Thereby, when a scheduling gain is obtained, a discrete arrangement is applied to signals destined for a remote terminal device and a nearby terminal device. On the other hand, when it is desired to reduce the amount of control information based on resource allocation information, or when it is desired to increase the number of terminals that can participate in DL-NOMA by improving symbol level cancellation by spreading / despreading, a remote terminal device and a neighboring terminal Apply a continuous arrangement to the device. As a result, it is possible to perform control in consideration of the moving speed of the terminal, frequency selective fading, required control information amount, desired throughput, and the like.

  In addition, the program which operate | moves with the base station apparatus and terminal device which concern on this invention is a program (program which makes a computer function) which controls CPU etc. so that the function of the said embodiment concerning this invention may be implement | achieved. Information handled by these devices is temporarily stored in the RAM at the time of processing, then stored in various ROMs and HDDs, read out by the CPU, and corrected and written as necessary. As a recording medium for storing the program, a semiconductor medium (for example, ROM, nonvolatile memory card, etc.), an optical recording medium (for example, DVD, MO, MD, CD, BD, etc.), a magnetic recording medium (for example, magnetic tape, Any of a flexible disk etc. may be sufficient. In addition, by executing the loaded program, not only the functions of the above-described embodiment are realized, but also based on the instructions of the program, the processing is performed in cooperation with the operating system or other application programs. The functions of the invention may be realized.

  In the case of distribution in the market, the program can be stored and distributed in a portable recording medium, or transferred to a server computer connected via a network such as the Internet. In this case, the storage device of the server computer is also included in the present invention. Moreover, you may implement | achieve part or all of the terminal device and base station apparatus in embodiment mentioned above as LSI which is typically an integrated circuit. Each functional block of the receiving apparatus may be individually formed as a chip, or a part or all of them may be integrated into a chip. When each functional block is integrated, an integrated circuit controller for controlling them is added.

  Further, the method of circuit integration is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. In addition, when an integrated circuit technology that replaces LSI appears due to progress in semiconductor technology, an integrated circuit based on the technology can also be used.

  In addition, this invention is not limited to the above-mentioned embodiment. The terminal device of the present invention is not limited to application to a mobile station device, but is a stationary or non-movable electronic device installed indoors or outdoors, such as AV equipment, kitchen equipment, cleaning / washing equipment Needless to say, it can be applied to air conditioning equipment, office equipment, vending machines, and other daily life equipment.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and the design and the like within the scope not departing from the gist of the present invention are also claimed. Included in the range.

  The present invention is suitable for use in a terminal device, a base station device, a communication system, and a communication method.

101 Base station apparatus 102, 103 Terminal apparatus 201-1 to 201-2 Encoding section 202-1 to 202-2 Modulation section 203-1 to 202-2 Power control section 204 Addition section 205 Resource allocation section 206 Scheduling section 207 OFDM Signal generation unit 208 Transmission antenna 501 IFFT unit 502 CP addition unit 503 Wireless transmission unit 601 Reception antenna 602 OFDM reception signal processing unit 603 Resource extraction unit 604 Channel compensation unit 605 Demodulation unit 606 Cancellation unit 607 Decoding unit 608 Encoding unit 609 Modulation unit 610 Power control unit 611 Demodulation unit 612 Decoding unit 701 Radio reception unit 702 CP removal unit 703 FFT units 801-1 to 801-2 Encoding units 802-1 to 802-2 Modulation units 803-1 to 803-2 Power control units 804 Addition unit 805 Resource allocation unit 806 Scheduling unit 807 OFDM signal generating unit 808 transmitting antenna 809 spreading unit 1001 receiving antenna 1002 OFDM received signal processing unit 1003 resource extracting unit 1004 channel compensating unit 1005 demodulating unit 1006 canceling unit 1007 replica generating unit 1008 power control unit 1009 spreading unit 1010 Despreading unit 1011 Demodulating unit 1012 Decoding unit 1101-1 to 1101-2 Encoding unit 1102-1 to 1102-3 Modulating unit 1103-1 to 1103-3 Power control unit 1104-1 to 1104-2 Adding unit 1105-1 ˜1105-2 Resource allocation unit 1106 Scheduling unit 1107-1 to 1107-2 OFDM signal generation unit 1108-1 to 1108-2 Transmit antenna 1109 S / P conversion unit 1110 Duplicating unit 1111 Precoding unit 1201 ˜1201-2 Encoding unit 1202-1 to 1202-3 Modulation unit 1203-1 to 1203-3 Power control unit 1204 Addition unit 1205-1 to 1205-2 Resource allocation unit 1206 Scheduling unit 1207-1 to 1207-2 OFDM Signal generators 1208-1 to 1208-2 Transmitting antenna 1209 S / P converter 1210 Precoding units 1301-1 to 1301-2 Reception antennas 1302-1 to 1302-2 OFDM received signal processing units 1303-1 to 1303-2 Resource Extraction Unit 1304 MIMO Separation Units 1305-1 to 1305-2 Demodulation Units 1306-1 to 1306-2 Cancellation Unit 1307 Replica Generation Unit 1308 Power Control Unit 1309 Synthesis Units 131-1 to 1311-2 Demodulation Units 132-1 to 1312 -2 Decoding Units 1401-1 to 14-14 01-2 Encoding Units 1402-1 to 1402-2 Modulation Units 1403-1 to 1403-2 Power Control Unit 1404 Addition Units 1405-1 to 1405-2 Resource Allocation Unit 1406 Scheduling Unit 1407 OFDM Signal Generation Unit 1408 Transmitting Antenna 1409 Spreading switching section 1501 Reception antenna 1502 OFDM reception signal processing section 1503 Resource extraction section 1504 Channel compensation section 1505 Demodulation section 1506 Cancellation section 1507 Replica generation section 1508 Power control section 1509 Spread switching section 1510 Despread switching section 1511 Demodulation section 1512 Decoding section

Claims (8)

A base station apparatus that includes an addition unit that adds signals exceeding the number of transmission antenna ports at the same time and the same frequency, and transmits from one or more transmission antenna ports,
The base station apparatus characterized in that the adder adds signals generated by different transmission schemes.   The base station apparatus according to claim 1, wherein the signals generated by the different transmission schemes include a signal generated by spreading processing and a signal generated without applying spreading processing.   The base station apparatus according to claim 1, wherein the different transmission schemes include at least an SC-FDMA transmission scheme and an OFDM transmission scheme.   The base station apparatus according to claim 1, wherein the different transmission schemes include a transmission scheme for transmitting a plurality of streams and a transmission scheme for transmitting one stream.   The base station apparatus according to claim 1, wherein the different transmission schemes are determined based on resource allocation information. A terminal device that receives a signal obtained by adding signals generated by different transmission schemes exceeding the number of transmission antenna ports at the same time and the same frequency,
A demodulator that performs demodulation processing on at least one of the different transmission methods, a replica generator that generates a symbol replica based on an output of the demodulator, and a cancel that subtracts the symbol replica from the received signal A terminal device.   The terminal apparatus according to claim 6, further comprising a despreading unit that performs a despreading process on at least one of the different transmission schemes.   The terminal apparatus according to claim 6 or 7, wherein the demodulation unit outputs a soft decision value, and the replica generation unit generates a soft replica.

Images